Throughout the pregnancy the fetus obtains nutrients and oxygen from the mother's blood, by transfer in the placenta to its own umbilical cord blood, and it excretes waste products of metabolism by the same route in reverse.

Then these bacteria excrete organic material to the clam and the clam can use that organic material as a food source.

Usually, a pregnant woman with preeclampsia develops dangerously high blood pressure and begins excreting protein in the urine.